Non-spherical resin particles produced by seed polymerization are conventionally known. Comparative example 5 of Patent Document 1 and comparative example 1 of Patent Document 2 give examples that describe polymer particles shaped like a snowman.
Patent Document 3 describes cocoon-shaped polymer particles and discloses that the particles, when added to coating materials or cosmetics, effectively impart to them viscosity, light scattering, and other unique surface properties.
Patent Document 4 describes polymer particles with a recessed sectional shape having one notch part continued in the diameter direction, a mushroom shape, a semi-spherical shape, or a double-sided convex lens shape.